Neoplastic transformation produces many changes in cell physiology, some of which can be studied using morphologic techniques. We have used morphologic methods to study three transformation-related areas: 1) We have employed light microscopic immunocytochemistry to evaluate monoclonal antibodies for suitability as immunotoxin reagents for cancer chemotherapy. We adapted methods for light microscopic immunocytochemistry in whole tissues, using frozen human tissues, cryostat sections and peroxidase labeling methods. This standardized method has been used to evaluate HB-21 (a monoclonal antibody to the human transferrin receptor), anti-TAC (a monoclonal antibody to the human IL-2 receptor), and other monoclonal antibodies generated against human ovarian cancer cell lines. 2) We have studied the phenomenon of multidrug-resistance (MDR) in cultured cells and morphologically examined the accumulation of the chemotherapeutic drug daunomycin. Using this drug as a fluorescence marker of drug accumulation in cells in culture, photometric microscopy studies of nuclei in individual cells showed that MDR cells have an accelerated efflux mechanism that is energy-dependent. This rapid morphologic assay has made it possible to evaluate multiple drugs for their effects on this efflux activity, and has shown major inhibition of daunomycin efflux by verapamil, quinidine, and vinblastine. 3) We have used immunocytochemical methods to localize some major proteins in transformed cultured cells. We have localized "p55", a major protein in cells that shows thyroid hormone binding activity, and "p86", a cytosolic heat-shock protein present in large amounts in many cells and identified as a tumor-specific transplantation antigen in animal systems. In other studies, preliminary experiments using single cell microinjection methods have demonstrated a specific inhibition of epidermal growth factor receptor synthesis following injection of anti-sense RNA for the EGF receptor gene.